Watercress...

[Jessiebean]

I have found water cress in a pond in the forest (really a sparsely wooded reclaimed rubbish dump the council calls a forest) and I was wondering if it is safe to eat as I have read that I could get nasty parasites from doing so...do others think it is worth the risk ( I saw fit to eat soft cheese and sushi during pregnancy after reading up on the risks)...

[CasperCastle]

From my limited knowledge about wild watercress, Liver-Fluke is the thing you need to be cautious of... so do a little research into that.
I'm sure I read somewhere that cooking it dramatically reduces the risk though, but don't take that as gospel!

This just came up in a quick search.

June Fanning - University College Dublin

Liver fluke (Fasciola hepatica) is a parasite or 'body-snatcher' that infects livestock worldwide, in particular cattle and sheep. Liver fluke is a significant welfare and economic concern as almost half the cattle and sheep in Ireland are infected. It also infects man – most commonly from ingestion of unwashed watercress.

The liver fluke has a complex life cycle. The adult parasite, in the host's liver, is a hermaphrodite (has both sex organs) and lays the eggs. The eggs are passed into the intestines and onto the pasture in the host's faeces. The eggs hatch and the first larval stage emerge. What happens next is crucial to the survival and development of the larvae. These tiny larvae have to find and infect an intermediate host (a mud snail) in order to feed, multiply and grow into the stage that infects cattle and sheep. The larvae are attracted to chemicals released by the mud snail and penetrate the snail's skin. For every one larva that enters the mud snail, up to 600 infective stages can emerge after a number of weeks. These then encyst, for protection from the elements, and wait on the grass (or watercress!) to be ingested by the final host (cattle, sheep, man).


After ingestion, the parasites migrate to the liver through the wall of the small intestine. The adult parasites live, eat and breed in the liver of the host animal. They burrow through the liver, digesting the tissue, and leaving paths of destruction in their wake. This damage to the liver causes serious disease, even death. The liver fluke release enzymes to help them digest the liver tissue. These enzymes are crucial to the nourishment and survival of the liver fluke. This parasite is capable of chronic infection and possesses an array of sophisticated strategies for avoiding and modulating the host's defence mechanisms (immune response).

Currently, infected animals are treated with anti-parasitic drugs. Unfortunately, these conventional weapons are becoming redundant due to increasing resistance of liver fluke to these drugs. In the absence of new drugs to combat the resistant fluke, there is a growing need to provide an alternative method of controlling the parasite.

J

[AnnaD]

Don't collect watercress unless it is growing in fresh running water. As Casper says, Liver fluke can be very nasty. Also, if you do find any growing by running water, always cook it first. That way anything unpleasant will be killed.

We are fortunate enough to have an abundance of watercress growing in a stream nearby, and the water is straight from a spring, so we know it's safe. If I saw it anywhere else, I wouldn't use it.